'\" t
.TH "SD_BUS_REQUEST_NAME" "3" "" "systemd 256.7" "sd_bus_request_name"
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.SH "NAME"
sd_bus_request_name, sd_bus_request_name_async, sd_bus_release_name, sd_bus_release_name_async \- Request or release a well\-known service name on a bus
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-bus\&.h>
.fi
.ft
.HP \w'typedef\ int\ (*sd_bus_message_handler_t)('u
.BI "typedef int (*sd_bus_message_handler_t)(sd_bus_message\ *" "m" ", void\ *" "userdata" ", sd_bus_error\ *" "ret_error" ");"
.HP \w'int\ sd_bus_request_name('u
.BI "int sd_bus_request_name(sd_bus\ *" "bus" ", const\ char\ *" "name" ", uint64_t\ " "flags" ");"
.HP \w'int\ sd_bus_request_name_async('u
.BI "int sd_bus_request_name_async(sd_bus\ *" "bus" ", sd_bus_slot\ **" "slot" ", const\ char\ *" "name" ", uint64_t\ " "flags" ", sd_bus_message_handler_t\ " "callback" ", void\ *" "userdata" ");"
.HP \w'int\ sd_bus_release_name('u
.BI "int sd_bus_release_name(sd_bus\ *" "bus" ", const\ char\ *" "name" ");"
.HP \w'int\ sd_bus_release_name_async('u
.BI "int sd_bus_release_name_async(sd_bus\ *" "bus" ", sd_bus_slot\ **" "slot" ", const\ char\ *" "name" ", sd_bus_message_handler_t\ " "callback" ", void\ *" "userdata" ");"
.SH "DESCRIPTION"
.PP
\fBsd_bus_request_name()\fR
requests a well\-known service name on a bus\&. It takes a bus connection, a valid bus name, and a flags parameter\&. The flags parameter is a combination of zero or more of the following flags:
.PP
\fBSD_BUS_NAME_ALLOW_REPLACEMENT\fR
.RS 4
After acquiring the name successfully, permit other peers to take over the name when they try to acquire it with the
\fBSD_BUS_NAME_REPLACE_EXISTING\fR
flag set\&. If
\fBSD_BUS_NAME_ALLOW_REPLACEMENT\fR
is not set on the original request, such a request by other peers will be denied\&.
.sp
Added in version 209\&.
.RE
.PP
\fBSD_BUS_NAME_REPLACE_EXISTING\fR
.RS 4
Take over the name if it was already acquired by another peer, and that other peer has permitted takeover by setting
\fBSD_BUS_NAME_ALLOW_REPLACEMENT\fR
while acquiring it\&.
.sp
Added in version 209\&.
.RE
.PP
\fBSD_BUS_NAME_QUEUE\fR
.RS 4
Queue the acquisition of the name when the name is already taken\&.
.sp
Added in version 209\&.
.RE
.PP
\fBsd_bus_request_name()\fR
operates in a synchronous fashion: a message requesting the name is sent to the bus broker, and the call waits until the broker responds\&.
.PP
\fBsd_bus_request_name_async()\fR
is an asynchronous version of
\fBsd_bus_request_name()\fR\&. Instead of waiting for the request to complete, the request message is enqueued\&. The specified
\fIcallback\fR
will be called when the broker\*(Aqs response is received\&. If the parameter is specified as
\fBNULL\fR
a default implementation is used instead which will terminate the connection when the name cannot be acquired\&. The function returns a slot object in its
\fIslot\fR
parameter \(em if it is passed as non\-\fBNULL\fR
\(em which may be used as a reference to the name request operation\&. Use
\fBsd_bus_slot_unref\fR(3)
to destroy this reference\&. Note that destroying the reference will not unregister the name, but simply ensure the specified callback is no longer called\&.
.PP
\fBsd_bus_release_name()\fR
releases an acquired well\-known name\&. It takes a bus connection and a valid bus name as parameters\&. This function operates synchronously, sending a release request message to the bus broker and waiting for it to reply\&.
.PP
\fBsd_bus_release_name_async()\fR
is an asynchronous version of
\fBsd_bus_release_name()\fR\&. The specified
\fIcallback\fR
function is called when the name has been released successfully\&. If specified as
\fBNULL\fR
a generic implementation is used that ignores the result of the operation\&. As above, the
\fIslot\fR
(if non\-\fBNULL\fR) is set to an object that may be used to reference the operation\&.
.PP
These functions are supported only on bus connections, i\&.e\&. connections to a bus broker and not on direct connections\&.
.SH "RETURN VALUE"
.PP
On success, these calls return 0 or a positive integer\&. On failure, these calls return a negative errno\-style error code\&.
.PP
If
\fBSD_BUS_NAME_QUEUE\fR
is specified,
\fBsd_bus_request_name()\fR
will return 0 when the name is already taken by another peer and the client has been added to the queue for the name\&. In that case, the caller can subscribe to
"NameOwnerChanged"
signals to be notified when the name is successfully acquired\&.
\fBsd_bus_request_name()\fR
returns > 0 when the name has immediately been acquired successfully\&.
.SS "Errors"
.PP
Returned errors may indicate the following problems:
.PP
\fB\-EALREADY\fR
.RS 4
The caller already is the owner of the specified name\&.
.RE
.PP
\fB\-EEXIST\fR
.RS 4
The name has already been acquired by a different peer, and SD_BUS_NAME_REPLACE_EXISTING was not specified or the other peer did not specify SD_BUS_NAME_ALLOW_REPLACEMENT while acquiring the name\&.
.RE
.PP
\fB\-ESRCH\fR
.RS 4
It was attempted to release a name that is currently not registered on the bus\&.
.RE
.PP
\fB\-EADDRINUSE\fR
.RS 4
It was attempted to release a name that is owned by a different peer on the bus\&.
.RE
.PP
\fB\-EINVAL\fR
.RS 4
A specified parameter is invalid\&. This is also generated when the requested name is a special service name reserved by the D\-Bus specification, or when the operation is requested on a connection that does not refer to a bus\&.
.RE
.PP
\fB\-ENOTCONN\fR
.RS 4
The bus connection has been disconnected\&.
.RE
.PP
\fB\-ECHILD\fR
.RS 4
The bus connection has been created in a different process than the current one\&.
.RE
.SH "NOTES"
.PP
Functions described here are available as a shared library, which can be compiled against and linked to with the
\fBlibsystemd\fR\ \&\fBpkg-config\fR(1)
file\&.
.PP
The code described here uses
\fBgetenv\fR(3), which is declared to be not multi\-thread\-safe\&. This means that the code calling the functions described here must not call
\fBsetenv\fR(3)
from a parallel thread\&. It is recommended to only do calls to
\fBsetenv()\fR
from an early phase of the program when no other threads have been started\&.
.SH "HISTORY"
.PP
\fBsd_bus_request_name()\fR
and
\fBsd_bus_release_name()\fR
were added in version 209\&.
.PP
\fBsd_bus_request_name_async()\fR
and
\fBsd_bus_release_name_async()\fR
were added in version 237\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-bus\fR(3), \fBsd_bus_new\fR(3), \fBsd_bus_slot_unref\fR(3)
